>>Dr. Ketchum: In this video we will focus on the functional anatomy of the male reproductive
system. Let’s begin by simply identifying structures that are important in the male
reproductive system. These include the vas deferens, also called the ductus deferens, the penis,
the testes—note that only one testicle is shown in this diagram—the scrotum,
the bulbourethral gland, the prostate gland, and finally, the seminal vesicle. You have
to have a basic understanding of location in order to understand function and how all these structures
work together. We will begin with the testes—the male gonad. This is a diagram of a longitudinal
section through one testicle so you can now see what’s inside. Notice that the majority
of the testicle is composed of seminiferous tubules. These tubules produce sperm via spermatogenesis,
but how? Let’s take a closer look. In order to do this, we need to zoom in on the seminiferous
tubule and take a cross-section through the tubule. Imagine taking a garden hose and cutting
it in half; this would be similar to cutting the tubule in half and looking at what’s
inside. The lumen of the seminiferous tubule is lined by cells called Sertoli cells. These
Sertoli cells are connected via tight junctions. Lining the outside of the Sertoli cells is
a layer of smooth muscle. Outside of the Sertoli cells are the Leydig cells; these are all
the cells that are really important. In addition to these structures, you will need to be familiar
with the following compartments: the basal compartment and the lumenal compartment. These
compartments are basically talking about regions of the cross-section. If we are talking about
the basal compartment, we are talking about the area that goes from the tight junction
toward that smooth muscle. And if we are talking about the lumenal compartment, we are talking
about the area that goes from the tight junction toward the lumen. Now that you are familiar
with the structures, let’s focus on their functions. We begin with the Leydig cells,
also called interstitial cells. The Leydig cells secrete testosterone. The Sertoli cells
support sperm development, or what is referred to as spermatogenesis. The smooth muscle surrounding
the Sertoli cells allows for peristalsis. This process is important, as it will propel
sperm through the seminiferous tubules. Well that’s all fine and dandy that the Sertoli
cells produce the sperm, but how do the sperm get out of the seminiferous tubules, and out
of the testes? This is our next goal. So here are the sperm and the seminiferous tubules.
The sperm has been produced by the Sertoli cells and released into the lumen of the seminiferous
tubule. Those sperm then travel through this little region here called the Rete testes,
and into the efferent ductules. This is the point and which the sperm exist the testes.
From the efferent ductules the sperm enter the epididymis, and will ultimately make their
way to the vas deferens. So that is the pathway the sperm are taking to get out of the testes.
What propelled the sperm through all those structures? Peristalsis. Now the sperm are
in the vas deferens, right? The vas deferens connects with the seminal vesicles to form
the ejaculatory duct. At this point, the sperm is mixed with fluid that came from the seminal
vesicles. The ejaculatory duct penetrates through the prostate gland to join the urethra.
As such, the sperm wind up in the urethra which receives substances from the bulbourethral
glands. Thus, both urine and sperm are in the urethra. So that was just the pathway
that the sperm take from the seminiferous tubules to the urethra. Now let’s look more
closely at the accessory glands I mentioned earlier. The seminal vesicles secrete an alkaline
fluid that contains fructose, enzymes, and prostaglandins. Remember, alkaline fluids
are basic. The purpose of this alkaline fluid is to neutralize the acid that is in the female reproductive
tract. The fructose is used for energy. Remember sperm have to swim, so they need energy for
motility. The enzymes in the fluid facilitate semen clotting. There are also prostaglandins
in this fluid; these are for motility and viability of the sperm. The prostate gland
is another accessory gland. The prostate gland secretes citrate, which is an energy source
for sperm motility and enzymes that will break down the semen clot once it is in the female
reproductive tract. Okay, so take a second to make sure you understand. The semen clots
during ejaculation, and is then broken down once it’s insid the female reproductive
tract. The last accessory gland is the bulbourethral glands. These glands secrete a fluid that contain
mucus. Why is mucus important? It serves as a lubricant.